The proposed research will involve a kinetic analysis of the subunit assembly process of both normal (Hb A, Hb F, Hb A2) and abnormal (Hb S, Hb E) hemoglobins. This process involves the combination of two unlike subunits to form the Alpha Beta dimer which then aggregates to form Alpha 2 Beta 2 tetramer. The isolated heme subunits themselves are oligomeric, adding an additional step of complexity to the overall process. Since the absorption spectrum of the isolated heme chains is distinct from that of the intact hemoglobin tetramer, the above reactions can be monitored using either a recording spectrophotometer or a stopped flow apparatus. The Alpha Beta dimer aggregation process will be also investigated in two modified hemoglobins which exhibit enhanced stability of their liganded tetramers. This research scheme will also evaluate the role of globin-heme reaction in the overall assembly process. It is unknown where during the formation of the tetramer the heme moiety is inserted into the polypeptide chain, but addition of this prosthetic group is essential for hemoglobin stability and function. The kinetics of the globinheme reaction can be monitored spectrophotometrically in a stopped flow device. The proposed work will involve a comparison of the rates of heme binding and protein folding of apohemoglobin (Alpha 0 Beta 0), semi-hemoglobin (Alpha Heme Beta 0 or Alpha 0 Beta Heme) and globin chains (Alpha 0; Beta 0) from normal and sickle hemoglobin. The rate of assembly of the hemoglobin tetramer, as well as the rate of insertion of the heme moiety, may be important post-translational determinants of the distribution of hemoglobins in the erythrocytes of normal individuals and those with various hematological disorders.